This 4.5km-long submersible causeway, in use since the 17C, was the only way for vehicles to reach the island from the late 19C until 1971, when the toll bridge was opened. Shoals formed the Gois causeway; the name is derived from a local term, goiser, meaning to wade. Floats are provided along the way so that people caught by the rapidly rising waters can pull themselves to safety and wait for the tide to turn.